Buggy code:
public class GaeXStream extends XStream { public GaeXStream ( PureJavaReflectionProvider pureJavaReflectionProvider , XppDriver xppDriver , ClassLoaderReference classLoaderReference ) { } @ Override protected void setupConverters ( ) { Mapper mapper = getMapper ( ) ; ReflectionProvider reflectionProvider = getReflectionProvider ( ) ; final ReflectionConverter reflectionConverter = new ReflectionConverter ( mapper , reflectionProvider ) ; registerConverter ( reflectionConverter , PRIORITY_LOW ) ; registerConverter ( new com . thoughtworks . xstream . converters . reflection . SerializableConverter ( mapper , reflectionProvider ) , PRIORITY_LOW ) ; registerConverter ( new com . thoughtworks . xstream . converters . reflection . ExternalizableConverter ( mapper ) , PRIORITY_LOW ) ; registerConverter ( new NullConverter ( ) , PRIORITY_VERY_HIGH ) ; registerConverter ( new IntConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new FloatConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new DoubleConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new LongConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new ShortConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( ( ( Converter ) ( new CharConverter ( ) ) ) , PRIORITY_NORMAL ) ; registerConverter ( new BooleanConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new ByteConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new StringConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new StringBufferConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new DateConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new BitSetConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new URLConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new BigIntegerConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new BigDecimalConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new com . thoughtworks . xstream . converters . collections . ArrayConverter ( mapper ) , PRIORITY_NORMAL ) ; registerConverter ( new CharArrayConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new com . thoughtworks . xstream . converters . collections . CollectionConverter ( mapper ) , PRIORITY_NORMAL ) ; registerConverter ( new com . thoughtworks . xstream . converters . collections . MapConverter ( mapper ) , PRIORITY_NORMAL ) ; registerConverter ( new com . thoughtworks . xstream . converters . collections . TreeMapConverter ( mapper ) , PRIORITY_NORMAL ) ; registerConverter ( new com . thoughtworks . xstream . converters . collections . TreeSetConverter ( mapper ) , PRIORITY_NORMAL ) ; <START_BUG> registerConverter ( new EncodedByteArrayConverter ( ) , PRIORITY_NORMAL ) ; <END_BUG> registerConverter ( new FileConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new com . thoughtworks . xstream . converters . extended . DynamicProxyConverter ( mapper , getClassLoader ( ) ) , PRIORITY_NORMAL ) ; registerConverter ( new com . thoughtworks . xstream . converters . extended . JavaClassConverter ( getClassLoader ( ) ) , PRIORITY_NORMAL ) ; registerConverter ( new com . thoughtworks . xstream . converters . extended . JavaMethodConverter ( getClassLoader ( ) ) , PRIORITY_NORMAL ) ; registerConverter ( new LocaleConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new GregorianCalendarConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new UUIDConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new EnumConverter ( ) , PRIORITY_NORMAL ) ; registerConverter ( new com . thoughtworks . xstream . converters . reflection . SelfStreamingInstanceChecker ( reflectionConverter , this ) , PRIORITY_NORMAL ) ; } }

Fix:
registerConverter ( ( ( Converter ) ( new EncodedByteArrayConverter ( ) ) ) , PRIORITY_NORMAL ) ;